This is such a good piece of homebrew, oh my God.
I'm only 1/4th way in and I'm loving it so far. I especially like the DM's tips, insight about balance philosophy and reasoning behind certain choices, and the extensive changelog at the bottom of the document. Really helps me better understand how to look at the class and evaluate it.
The only point of detriment is that the format you chose, that of a Google docs that is, is really hostile for such long brews. I would recommend switching to homebrewery or GM Binder. You could turn those 100 pages into a 30-ish page document very easily, and it would be much more digestible for people to read.
(Btw, I remembered your username from that discussion about dragons, and I agreed with you back then. Despite their prominence in fantasy imagery, they are really underutilized as character companions or as a playable race. I'm glad to see your passion for the topic translated into this!)